The present invention relates to a power supply apparatus, a charge control apparatus, a charge control method, a computer, and an electric automobile; more particularly the invention is directed to a power supply apparatus equipped with a rechargeable battery, a charge control apparatus for controlling the charging of the battery provided in the power supply apparatus, a charge control method, a computer to which the charge control method is applied, and an electric automobile equipped with the power supply apparatus and the charge control apparatus.
It is well known that mobile computing has become evermore pervasive, and, as a result, portable personal computers (hereinafter referred to as portable PCs) now have various sizes and diverse functions. Examples of these pervasive portable PCs include notebook PCs, palmtop PCs, and PDAs (Personal Data Assistants).
A portable PC typically includes a battery in the main body thereof. Due to the presence of a stored battery, storage battery or battery component (hereinafter referred to a stored battery) with a portable PC, even in an environment in which no commercial power supply is available, for instance, in a mobile environment such as a train, the user can use and operate the portable PC. Typically, in conjunction with the stored battery, a secondary battery is usually also employed which can be used repeatedly by charging.
With regard to the secondary battery, which can be used in computers such as the portable PC, various household electric appliances, and electric automobiles, it is known that an intelligent version of the battery can also be used wherein the intelligent battery may typically have a built-in electric circuit. In accordance with such a battery, the remaining capacity of the battery can be informed (e.g. by display) to the outside or external portion of the battery with a relatively high degree of accuracy due to the built-in electric circuit of the battery. Accordingly, for instance, by using the intelligent battery as the secondary battery for a portable PC, the user can anticipate in advance of the actual exhaustion of the battery as to how much of the remaining capacity is left during the use of the portable PC in an environment that does not allow the use of a commercial power source, so as to avoid a sudden shutdown of the PC during the use.
On the other hand, when both the secondary battery, as mentioned above, and an AC adapter for converting power by a commercial power source to power suitable for the side to be supplied with power are concurrently connected, it is usually designed to carry out the charging so that the battery capacity of the secondary battery always maintains 100%. However, there can be a problem that the chemical reaction in the battery accelerates and the secondary battery deteriorates in a shorter period of time than normal when the battery capacity is reduced by self-discharge where the charge is always maintained at 100% by active recharging.
Further, if the secondary battery is removed from the side to be supplied with power and preserved for a long period, self-discharging can occur, and as a result, it may be preserved in a completely discharged state; in this situation, a problem may occur in which the chemical reaction in the battery accelerates causing the secondary battery to deteriorate in a shorter period of time.
That is, generally a secondary battery has a battery capacity range suitable for preservation according to the type or the like of the secondary battery, and preservation in the battery capacity range is recommended by each secondary battery maker, though the progress of deterioration is accelerated if the secondary battery is preserved with a battery capacity being outside the range.
One technique which attempts to overcome the above problem is described in Published Unexamined Patent Application No. 8-33220, which is incorporated herein by reference.
In accordance with that technique, once the type of a removably structured secondary battery is determined, the charging and discharging of the battery are controlled to provide a capacity suitable for preservation of the secondary battery thereby suppressing the overall deterioration of the secondary battery in the preservation.
However, the technique described in the above-mentioned Published Unexamined Patent Application No. 8-33220 is limited in that it requires a means for determining the type of the secondary battery, whereby this means likely pushes the overall cost of the resulting component upwards. This additional means and additional cost are unnecessary and undesired results in attempting to overcome problems in the field, such as that described above.
Further, in the technique described in the above Published Unexamined Patent Application No. 8-33220, if the mode automatically switches to a preservation mode, the period of idle state of the secondary battery is measured by a timer that is provided external to the secondary battery; the preservation mode is entered when the duration of idle state reaches a predetermined period. However, when this technique is applied to an apparatus such as a portable PC that selectively uses the power of either the commercial power source or the secondary battery, and, in addition, the above timer is included in the apparatus, then the timer is reset if the AC adapter provided to supply commercial power to the apparatus is pulled out, so the mode cannot switch to the preservation mode with accurate timing. This result is also undesired to overcome the problems in the field.
The present invention is directed to a power supply apparatus in which deterioration of the power supply apparatus during its preservation can be suppressed at low cost while providing reliability. The present invention is also directed to providing a charge control apparatus and charge control method which can suppress the deterioration of the power supply apparatus during the preservation of the power supply apparatus at low cost while providing reliability. The present invention is further directed to providing a computer and an electric automobile to which the charge control method of the present invention can be applied.
The power supply apparatus according to the present invention is provided as an intelligent battery with a rechargeable battery and charge demanding means. The above rechargeable battery is inclusive, inter alia, of all secondary batteries such as lithium-ion battery, nickel-hydrogen battery, nickel-cadmium battery, and lithium-polymer battery. Further, the charge demanding means is inclusive of but not limited to an electric circuit such as a CPU (Central Processing Unit).
It In one aspect of the present invention for a power supply apparatus, a charge demand is output when the remaining capacity of the battery is detected, by the charge demanding means, and the remaining capacity becomes lower than a predetermined preservation capacity value or range which is suitable for preserving the battery.
The remaining battery capacity may be detected, for instance, by previously determining and storing the full-charge capacity, and then subtracting the discharge amount since the time of full-charge from the full-charge capacity value. Further, in relation to the remaining battery capacity, the voltage value of the battery which often increases or decreases depending on the remaining capacity, may be utilized.
Further, in an aspect of the present invention, the power supply apparatus is not connected to a load to,be supplied with power from the battery (i.e., the invention is of the form in which power is not supplied to the load though the apparatus is connected to the load, etc.). Furthermore, the preservation capacity is defined to include a single capacity value, as well as a capacity range having an upper limit capacity value and a lower limit capacity value. A charge demand is output when the remaining battery capacity becomes lower than the lower limit capacity value of the preservation capacity range.
Since the characteristics of a battery provided in the power supply apparatus may vary differently depending on the differences in technology, maker, and material, the preservation capacity is directly dependent on the specific battery. Thus, in the power supply apparatus according to the present invention, with a predetermined preservation capacity suitable for preserving the battery as a standard, a charge demand is output when the remaining battery capacity becomes lower than the preservation capacity.
As described above, in the power supply apparatus according to the present invention, the remaining capacity of the battery may be detected, and a charge demand is output when the remaining capacity becomes lower than the predetermined preservation capacity suitable for battery preservation. Since the power supply apparatus itself determines the timing of charging (recharging) for maintaining the preservation capacity according to the battery, the battery can be maintained at the preservation capacity suitable for preserving the battery by only externally charging the battery when the charge demand is output, without providing any means for determining the battery type, so the battery deterioration in preservation can be suppressed at low cost.
Further, in another aspect of the present invention, the charge demanding means may include output means which outputs information indicating a charge current value for the battery as the charge demand. In this case, by the output means, information indicating a charge current value for the battery is output as the charge demand. In this aspect, since it is only needed to zero the charge current value if no charge demand is output, the output/non-output of charge demand can be readily switched and a proper charge current value according to the battery can be output to the outside, so proper charging to the battery can be realized.
Furthermore, in another aspect, the charge demanding means may further include a detecting means for detecting the use state of the battery and measuring means for measuring the duration of idle state of the battery, so that the charge demand is output when the remaining capacity is lower than the preservation capacity and the idle state is equal to or longer than a predetermined time. In this case, the use state of the battery is detected by the detecting means, and the duration of idle state of the battery is measured by the measuring means based on the detected result, and the charge demand is output when the remaining capacity is lower than the preservation capacity and the idle state is equal to or longer than the predetermined time.
In addition, the use state of the battery that is detected by the detecting means indicates a state in which power is supplied to a load, and the idle state indicates a state in which no power is supplied to the load. And, determination as to whether or not the battery is in the idle state can be made, for instance, by detecting the output current from the battery, and deciding that it is in the idle state if the output current is smaller than an output current that can be considered supplying power to the load.
In accordance with the power supply apparatus in this aspect, the charge demand for the remaining battery capacity being lower than the preservation capacity is output only when the idle state becomes equal to or longer than the predetermined time, and the power supply apparatus itself automatically makes the switch to a mode for maintaining the battery at a remaining capacity suitable for preservation (corresponding to the above-mentioned preservation mode), so deterioration in the preservation can reliably be suppressed even if the AC adapter provided for supplying commercial power to the load is pulled out.
Moreover, in still another aspect, the charge demanding means may further include a setting means for making a setting enabling a charge demand to be output, so that the charge demand is output when the remaining capacity is lower than the preservation capacity and the setting is made by the setting means to enable the charge demand to be output.
In this aspect, since a configuration is provided in which the setting can be externally made by the setting means to enable the charge demand to be output, the power supply apparatus can be switched to the preservation mode if the user sets a switching to the preservation mode by a utility program or the like.
In another aspect of the present invention, the charge control apparatus and charge control method control the charging of the battery provided in the power supply apparatus, and control the battery charge operation by a charger in response to a charge demand from the power supply apparatus.
In accordance with the charge control apparatus and charge control method according to the present invention, since the battery charge operation by the charger is controlled in response to the charge demand that is output from the power supply apparatus according to the present invention, the battery of the power supply apparatus can be maintained at a preservation capacity suitable for preserving the battery without providing means for determining the battery type, so the battery deterioration in the preservation can be suppressed at low cost.
Furthermore, in another aspect, the charge control apparatus and charge control method according to the present invention may read the remaining battery capacity by the charge demanding means according to the present invention, and if the read remaining capacity exceeds the preservation capacity, the battery is discharged to the preservation capacity before the charge operation.
This allows the remaining battery capacity to be rapidly reduced to the preservation capacity, and switching to the preservation mode can be made in a short time.
In another aspect of the present invention, the application of the charge control method to a computer including a CPU, a memory, a display, an input device, which are interconnected by a bus, and the power supply apparatus can be implemented by making the above memory a machine-readable recording medium having recorded thereon a program that controls the charging of the power supply apparatus according to the charge control method of the present invention. In accordance with this computer, since the battery charge operation by the charger is controlled in response to a charge demand that is output from the power supply apparatus according to the present invention, the battery of the power supply apparatus can be maintained at a preservation capacity suitable for preserving the battery without providing means for determining the battery type, so the battery deterioration in the preservation can be suppressed at low cost.
Further, the application of the charge control method according to the present invention to a computer including a CPU, a memory, a display. an input device, a network connection device, which are interconnected by a bus, and the power supply apparatus according to the present invention can be implemented by making the external storage of a server (referenced as 41 in FIG. 1) computer arranged on a network, to which the network connection device is connected, a machine-readable recording medium having recorded thereon a program that controls the charging of the power supply apparatus according to the charge control method of the present invention. In accordance with this computer, since the battery charge operation by the charger is controlled in response to a charge demand that is output from the power supply apparatus according to the present invention, the battery of the power supply apparatus can be maintained at a preservation capacity suitable for preserving the battery without providing means for determining the battery type, so the battery deterioration in the preservation can be suppressed at low cost.
Further, by providing at least one of the power supply apparatus and the charge control apparatus according to the present invention in an electric automobile (depicted as 900 in FIG. 12), the effect similar to the charge control apparatus according to tie present invention can also be produced for an electric mobile device such as tin electric automobile.